Sea plants regulate oxygen level.

Scientists have discovered a natural mechanism by which atmospheric oxygen is regulated, even if it has been upset by natural or other factors. According to University of Texas at Austin marine scientist Ellery Ingall and Philippe Van Cappellen of Georgia Institute of Technology, oxygen, phosphorus, and the microscopic marine plants known as phytoplankton are involved. A global balance is maintained in the atmospheric oxygen level that ultimately depends on the plankton productivity. Like all plants, phytoplankton produce molecular oxygen as part of photosynthesis.

"There are a number of basic reactions living in the ocean, but probably the most important for us is phytoplankton production," explains Ingall. "That's because plants take up [CO.sub.2] and give off oxygen." The rise in the productivity of plankton living in the ocean results in a greater amount of the plant material falling to the ocean bottom and decaying. In doing so, the material consumes oxygen.

The depletion of the oxygen stimulates the release of phosphorus from the ocean sediments through various chemical and biological reactions. The phosphorus is an important nutrient for phytoplankton, and increases...